By placing the CPU and the tiny 16 by 16 pixels screen in the cartridge and not the console, Jay Smith managed to create the very first handheld gaming machine back in 1981: the Milton Bradley Microvision. Sadly the tech and cost limitations of the time meant the Microvision failed to become a success and only got 12 games released for it.
On the other hand, you can bid on eight of those game and the console (which comes with one more game, Blockbuster) to play them on via this MB Microvision eBay auction. Everything works great and comes in its original box. Baseball and Connect Four are sealed.
Seller ships only within the US.